Freshwater fish are in a constant battle with their environment when it comes to maintaining their electrolyte balance as they are continuously losing ions to the surrounding water. Therefore, they have to actively absorb ions such as sodium, calcium and chloride from the water (see figure below). Prior research has shown that acidic environments cause adult and larva zebrafish to increase sodium uptake from their environment.
Researchers Kumai et al (University of Ottowa, Ontario, Canada) have provided evidence to suggest that the intracellular signaling molecule cAMP can increase the uptake of sodium in zebrafish larvae following exposure to an acidic environment.
Kumai Y, Kwong RWM, Perry SF. The role of cAMP-mediated intracellular signaling in regulating Na uptake in zebraﬁsh larvae. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology. 306: R51-R60, 2014.